Relay

ABSTRACT

Relay having contact springs operated by a shifting member, which is mechanically held in one or two end positions. The shifting member is shiftable by one or two magnetic drive systems. It is provided with two over-center springs at one end or at each end. The over-center springs bear at one end on the movable shifting member and on the other end on a fixed point, which is connected to the body of the relay. Monostable relays are provided with a return spring.

BACKGROUND OF THE INVENTION

This invention relates to a relay having contact springs operated by ashifting member, which is mechanically held in one or two end positions.

Relays are known which comprise locking mechanisms, such as are used inso-called latch relays, in which the relay contacts are held in theirend positions by mechanical means. These locking mechanisms often occupya large space and are not highly reliable owing to abrasion.

The invention avoids these disadvantages and relates to a relay whichcan be used particularly in modern printed circuit technology and iscorrespondingly small.

SUMMARY OF THE INVENTION

The relay with shifting member according to the invention ischaracterized in that the shifting member is shiftable by one or twomagnetic driving systems by the armatures thereof, that the shiftingmember is provided with two over-center springs at one end or at eachend, that said over-center springs bear at one end on the movableshifting member and at the other end on a fixed point, which isconnected to the body of the relay, that said over-center springs whenprovided only at one end are provided at their other end with a returnspring, that in a relay comprising two magnetic driving systems thedifference between the distance between the abutment bearings of theshifting member and the distance between the fixed abutment bearings isbetween zero and substantially the length of the shifting movement ofthe shifting member and that in a relay comprising only one magneticdriving system the movable abutment bearings are substantially alignedwith the fixed abutment bearings and the shifting member has shouldersurfaces which are engaged by the contact springs and serve topositively constrain the latter.

To stabilize the constraint of the shifting member, it is a preferredfeature of the invention that the over-center springs consist of leafsprings. According to a preferred feature of the invention, these leafsprings may be omega-shaped and may be squarely cut or beaded at thebearing ends.

According to a preferred further feature of the invention, the abutmentbearings provided for the over-center springs in the movable member andin the fixed abutment are tub-shaped.

To avoid a false switching in case of a breakage of an over-centerspring, a preferred feature of the invention resides in that a guide isprovided in the shifting member and has offset cross-sections, and anelement fixedly connected to the yoke of the relay is guided in saidguide and in case of a canting of the shifting member due to a defectiveover-center spring engages the shoulder of the offset cross-section sothat this interengagement prevents a movement of the shifting member.

According to a preferred feature of the invention, screws are providedwhich serve to secure the relay yokes to the base for the relay springsand which are screwed into the relay yoke and have an extended headwhich is adapted to be inserted through a hole in the base for the relaysprings and has adjacent to the slot of the screw a smallercross-section defining an annular groove, which is adapted to receivewedges or wedge springs extending at right angles to the axis of thescrew for a final fixation.

Finally, according to a preferred feature of the invention, a reliableopening of contacts which have become welded together is enabled in thatthe fixed contact springs are embedded in plastics material as far as toa point which is close to the contact point, and the movable contactsprings are stiffened in and beyond the zone of the contact point inthat the cut side edges of the relay springs are beaded.

BRIEF DESCRIPTION OF THE DRAWING

Embodiments of the invention will now be explained more fully and by wayof example with reference to the drawing, in which

FIG. 1 is a portion of the relay according to the invention having twoend positions (bistable relay); in this relay, the fixed bearings areclose to each other;

FIG. 2 shows a portion of another relay according to the invention withtwo end positions, in which the fixed bearings are widely spaced apart.

FIG. 3 shows a portion of another relay according to the invention whichhas one end position (monostable relay).

FIGS. 4 and 5 show emodiments of the omega-shaped over-center spring.

FIG. 6 shows the tube-shaped bearings.

FIGS. 7 and 8 show how the shifting member is locked before and after abreakage of an over-center spring.

FIG. 9 shows the arrangement for the assembly.

FIGS. 10 and 11 show the insertion of clamping elements for clamping theassembled members in position.

FIG. 12 illustrates the reinforcement of the contacts and springs fortheir separation when they have become welded together.

FIGS. 13 to 15 show diagrammatically the positions of the over-centersprings in different arrangements of the bearings. Finally,

FIG. 16 shows diagrammatically the optimum dimensioning of the effectivesprings.

DESCRIPTION OF THE PREFERRED EMBODIMENT

According to FIG. 1, the response of the left-hand or right-handarmature causes the movable shifting member 1 to be shifted by thearmatures 2 and 3 to the right or left, respectively, beyond the centerof the possible stroke, and the shifting member then automaticallyengages all boundary surfaces 26 and 27. The shifting member 1 isconstrained to move parallel to itself by springs, preferably pairs ofleaf springs 4, 5 and 6, 7, respectively. The fixed part of the relaycontains on each side a projection 8 or 9. The shifting member 1 and theprojections 8 and 9 are formed with notches, in which the over-centersprings abut. The over-center spring 4 abuts in bearings 10 and 12, theover-center spring 5 in bearings 13 and 11, the over-center spring 6 inbearings 14 and 16 and the over-center spring 7 in bearings 17 and 15.These over-center springs cooperate so as to hold the shifting member 1in its left-hand and right-hand end positions, respectively. Detailsregarding the location of the bearings will be stated with reference toFIGS. 13 to 15. Notches 22 and 24 receive the projections 23 and 25 andserve to transmit the movement of the armatures 2 and 3 to the shiftingmember. The notches 22 and 24 and/or the projections 23 and 25 may beomitted so that the armature engages only a simple projection ratherthan a stepped projection. The armatures 2 and 3 may be duplicated onthe opposite side but this is not essential. The shifting member 1 hasshoulder surfaces 18 and 19 for actuating the contact springs 20 and 21.

Only two relay springs 20 and 21 are shown. Instead of two relaysprings, a plurality of pairs of relay springs or individual relaysprings may be provided. The contacts with which these movable relaysprings 20 and 21 cooperate are not visible and consist of fixedcontacts which are either disposed within the relay springs or entirelyor partly outside the same. The movable contact springs may be guided inchambers disposed within the shifting member, and these chambers mayalso be used as spark-breaking chambers.

When the shifting member 1 has been shifted by the armatures 2 and 3beyond the center and has then automatically shifted to one end positionor the other, the shifting member and the movable contacts shifted by itremain in this position even when the magnetic force ceases to act andthe armature no longer exerts a force. Only the other armature can shiftthe shifting member in the other direction to change the movablecontacts. In the latter case, a magnetic force is no longer requiredwhen the position beyond the center and the automatically assumed endposition have been reached and the exciting coil may then bedeenergized, whereas the shifting member does not continue to move. Thisoperation is described as bistable.

FIG. 2 shows an arrangement in which the movable and fixed bearings ofFIG. 1 are reversed. The shifting member 28 is again moved to the rightand left, respectively, by the armatures 29 and 30 through theintermediary of the projections 53 and 54 after which the shiftingmember arrives independently the areas of contact 47 and 48. Theover-center spring 31 abuts in bearings 39 and 40, the over-centerspring 32 in bearings 41 and 42, the over-center spring 33 in bearings43 and 44 and the over-center spring 34 in bearings 45 and 46. Thebearings are provided in extensions 35 and 36 of the shifting member andin the walls of the fixed members 37 and 38. The distances between thebearings are properly dimensioned as in FIG. 1; these dimensions will bedescribed with reference to FIGS. 13 to 15. Only two of the contactsprings, namely, 49 and 50, are shown. The contact springs cooperatewith fixed contacts, which are not shown and are provided on fixedcontact springs that are disposed within or entirely or partly outsidethe movable contact springs. The shifting member has shoulders 51 and 52for actuating the contact springs.

FIG. 3 shows the monostable embodiment of the relay according to theinvention. This embodiment agrees substantially with the left-hand halfof FIG. 1. Instead of the right-hand over-center springs, a returnspring 46 is provided, which cooperates with the shifting member 1. Inaddition to exerting a spring action, the return spring contrains theshifting member 1 to move parallel to itself. upon an actuation of thearmature 2, the shifting member 1 is shifted to the right by connectingmeans 22 and 23 against the force of the return spring 46 and inconsideration of the force of the relay springs 20 and 21 and of theover-center springs 4 and 5. The optimum dimensions of the severalsprings will be described more fully with reference to FIG. 16.

FIGS. 4 and 5 show an over-center spring consisting of an omega-shapedleaf spring. The ends are squarely cut in FIG. 4. To improve theguidance and to reduce the wear, the ends are beaded in FIG. 5. In themiddle the springs have almost the configuration of three-fourths of acircle whereas the annexed portions are straight. This configurationaffords the advantage that a large spring force can be accomodated in avery small space and the springs are reliably held in their bearings inall actuated positions and can be manufactured in a simple manner.

Optimum results will be obtained if the preferred end formation shown inFIG. 5 is combined with tub-shaped bearings as shown in FIG. 6. Forinstance, the notches of the abutment bearing 10 in the shifting member1 but possibly also those of the fixed bearings are internallytub-shaped so that the beaded end portions roll in the tubs and thusexert the smallest pressure per unit area in the stable position. Withthis design of the abutment bearings and of the ends of the overcentersprings, the wear will be minimized.

FIG. 7 shows means for preventing an actuation of the shifting member 1when over-center springs are defective. Upon a movement of the shiftingmember, a projection 60 or 61 in the fixed part of the relay enters arecess 54 or 55. Upon a breakage of an over-center spring, the shiftingmember 1 is automatically canted, as is apparent from FIG. 8, so thatthe projection, e.g. 60 engages the step 56 to prevent a continuedmovement of the shifting member 1 and a wrong actuation of the contacts.The steps 57, 58 and 59 are for the same purpose.

FIG. 9 shows how the relay is assembled in accordance with theinvention. The screw heads 62 and 63 are not easily accessible andcannot be tightened with a conventional screwdriver. The screws serve tohold the fixed body 66 or 67 of the relay and the yoke 64 or 65 of therelay trough the bore-holes 70 or 71 together. This is accomplished inaccordance with FIG. 10 by a wedge 72 and in accordance with FIG. 11 bya wedge spring 73, which are inserted into grooves 68 or 69 (not shown)on the head of the screw and by their wedge action clamp the screws inposition at right angles to the direction in which the screws areconventionally fixed. The screws are previously screwed into the yokeand extended trough a hole in the set of fixed relay springs.

FIG. 12 shows measures which facilitate the opening of contacts thathave become welded together, e.g., by an excessively high current. Suchcontacts would normally break and cause wrong switching operations. Thismeasure also results in a reliable blocking of the shifting member 1 ifthe contacts have become welded together so firmly that they cannot beopened by the forces available in the relay. This sequence is requiredto ensure that the contact system moves under positive constraint. Suchmovement under positive constraint is required, e.g., in relays forsafety functions. The fixed contact springs are embedded in plasticsmaterial to the highest possible level as is shown at 74. 75 and 76 areflangings on the movable contact-spring, which flangings serve for astiffening of the contact-zone and so obviate the risk of breaking.

FIGS. 13 to 15 show possible locations of the movable and fixed abutmentbearings, which are arranged in such a manner that a bistable behaviorof the shifting member is ensured by the four over-center springsstressed between the abutment bearings.

In the arrangement shown in FIG. 13, where the distances measuredbetween the movable abutment bearings 80, 84 and 83, 87 are as large asthose between the fixed abutments 81, 85 and 82, 86 and the over-centersprings 88 to 91 are aligned in both end positions, which are defined bythe engagement of the shifting member 77 with the boundary surfaces 78and 79 and in the unstable center position, i.e., throughout the strokeof the shifting member.

In FIG. 14, the distances measured between the movable abutment bearings95, 99 and 98, 102 are shorter than the distances between the fixedabutment bearings 96, 100 and 97, 101. The difference between thesedistances is substantially as large as the shifting movement of theshifting member 92 so that the movable and fixed abutment bearingsdisposed on the engaging side of the shifting member are substantiallyaligned in the stable positions, which are defined by the engagement ofthe shifting member with the boundary surfaces 93 and 94. Theover-center springs 103-106 are symmetrically arranged in the unstablecenter position of the shifting member.

In FIG. 15, the distances between the movable abutment bearings 109, 113and 112, 116 exceed the distances between the fixed abutment bearings110, 114 and 111, 115. The difference between these distances issubstantially as large as the length of the shifting member 121 so thatthe movable and fixed abutment bearings on the side opposite to theengaging side are substantially aligned in the stable positions definedby the engagement of the shifting member with the boundary surfaces 107and 108. The over-center springs 117 to 120 are symmetrically arrangedin the unstable center position of the shifting member.

FIG. 16 shows the force-displacement characteristic of a monostablerelay according to the invention, as is shown, e.g., in FIG. 3. In thediagram, the displacement s of the shifting member is plotted along thevertical axis and the force p required to move the shifting member isplotted along the horizontal axis.

The curve 122 represents the force which is exerted by the magnet systemon the shifting member in case of constant excitation. In an operativerelay, the magnetic force represented by curve 122 must exceed theopposing mechanical force which is to be overcome and which isrepresented by the curve 123. There is usually a critical point 126,always approximately at the center of the stroke, at which themechanical force curve contacts the magnetic force curve in the case ofa minimum excitation. It is apparent that there are force reserves 127and 128 at the beginning and end of the stroke and that there are noforce reserves at the center.

The mechanical characteristic 123 should conform as closely as possibleto the magnetic characteristic 122 so that the same force reserves areavailable in all parts. This is accomplished by the use of an opposingspring force, exerted by additional springs or in the arrangementaccording to the invention, by the omega-shaped overcenter springs,which are designed to exert no force at all in the initial position 130and approximately in the end position 129 whereas they exert a maximumassisting force 131 approximately at the center to compensate the powerreserve deficit. The sum of curves 123 and 124 is represented by curve125. As a result, the magnetic force characteristic 122 conforms closelyto the mechanical characteristic 123 so that the excitation requirementof the magnetic system and the energy consumption can be reduced.

We claim:
 1. A relay having contact springs operated by a shiftingmember which is mechanically held in either one or the other of two endpositions, comprising:a shifting member; a pair of magnetic drivesystems each of said magnetic drive systems including an armature forshifting said shifting member from one of said end positions to theother of said end positions; a pair of overcenter springs coupled tosaid shifting member at each end thereof such that said overcentersprings bear at one end on said movable shifting member and at the otherend on a fixed surface which is connected to said relay; abutmentbearing means on said shifting member and on said fixed surface arrangedsuch that one end of said overcenter springs bear on the abutmentbearing means on said shifting member and the other end of saidovercenter springs bear on the abutment bearing means on said fixedsurface, said abutment bearing means further arranged such that thedifference between the distance between the abutment bearing on saidshifting member and the distance between said fixed abutment bearings isbetween zero and substantially the length of the shifting movement ofsaid shifting member.
 2. A relay in accordance with claim 1 wherein saidovercenter springs are comprised of leaf springs for stabilizing theconstraint of said shifting member.
 3. A relay in accordance with claim2 wherein said overcenter springs are bent in omega-shape and aresquarely cut at the bearing ends thereof.
 4. A relay in accordance withclaim 2 wherein said leaf springs are bent in omega-shape and are beadedat the bearings ends thereof.
 5. A relay in accordance with claim 1wherein said abutment bearings for said overcenter springs in saidshifting member and on said fixed surface are tub-shaped.
 6. A relay inaccordance with claim 1 further comprising:guide means in said shiftingmember having offset cross-sections; and means fixedly connected to saidrelay in the yoke thereof which is guided in said guide for preventingfalse switching in the event of a breakage of an overcenter springwhereby said overcenter spring engages the shoulder of said offsetcross-section when said shifting member is canted to prevent movement ofsaid shifting member.
 7. A relay in accordance with claim 1 furthercomprising:means for securing said relay yokes to said fixed surface forsaid relay springs, said securing means having an extended portionadaptable to be inserted through a hole in said fixed surface for saidrelay springs and having a cross-section defining an annular groovewhich is adapted to receive wedges.
 8. A relay in accordance with claim1 wherein said fixed contact springs are imbedded in a plastic materialup to a point thereon which is close to the contact point to stiffensaid movable contact springs in and beyond the zone of the contact pointsuch that cutside edges of said relay springs are beaded whereby areliable opening of contacts which have become welded together isprovided.
 9. A relay having contact springs operated by a shiftingmember which is mechanically held in one end position, comprising:ashifting member; a magnetic drive system including an armature forshifting said shifting member from said one end position; a pair ofovercenter springs coupled to said shifting member at said one endthereof such that said overcenter springs bear at said one end on saidmovable shifting member and at the other end on a fixed surface which isconnected to said relay and which includes a return spring thereon; andabutment bearing means on said shifting member for receiving one end ofsaid overcenter springs and further abutment bearing means on said fixedsurface for receiving the other end of said overcenter springs andarranged such that the abutment bearings on said shifting member aresubstantially aligned with said further abutment bearings and saidshifting member includes shoulder surfaces which are engaged by contactsprings to constrain said shifting member.
 10. A relay in accordancewith claim 9 wherein said overcenter springs are comprised of leafsprings for stabilizing the constraint of said shifting member.
 11. Arelay in accordance with claim 10 wherein said overcenter springs arebent in omega-shape and are squarely cut at the bearing ends thereof.12. A relay in accordance with claim 10 wherein said leaf springs arebent in omega-shape and are beaded at the bearings ends thereof.
 13. Arelay in accordance with claim 9 wherein said abutment bearings for saidovercenter springs in said shifting member and on said fixed surface aretub-shaped.
 14. A relay in accordance with claim 9 furthercomprising:guide means in said shifting member having offsetcross-sections; and means fixedly connected to said relay in the yokethereof which is guided in said guide for preventing false switching inthe event of a breakage of an overcenter spring whereby said overcenterspring engages the shoulder of said offset cross-section when saidshifting member is canted to prevent movement of said shifting member.15. A relay in accordance with claim 9 further comprising:means forsecuring said relay yokes to said fixed surface for said relay springs,said securing means having an extended portion adaptable to be insertedthrough a hole in said fixed surface for said relay springs and having across-section defining an annular groove which is adapted to receivewedges.
 16. A relay in accordance with claim 9 wherein said fixedcontact springs are imbedded in a plastic material up to a point thereonwhich is close to the contact point to stiffen said movable contactsprings in and beyond the zone of the contact point such that cutsideedges of said relay springs are beaded whereby a reliable opening ofcontacts which have become welded together is provided.